摘要:

SummaryFish farming activities result often in considerable high organic loadings to the water masses and sediments near the fishfarm. This study was carried out to evaluate the potential of flounder as food spillage feeder in salmonid freshwater culture.When transferring to fresh water, a clear tendency of an obligate need for food was discovered. Sufficient and continuous amounts of food are absolutely necessary for survival also when the flounder has been adapted for freshwater as long as 15 months.Flounder both in cages and in trays seemed to have little or no problem feeding on the bottom deposits (food and remnants of salmon) naturally occurring in salmon smolt production units. A high feeding rate in 0+ flounder preying on different cladoceran species was observed in addition to no significant size electivity.When feeding 0+ flounder and salmon in duoculture with small amounts of zooplankton, a competition effect resulting in growth inhibition in salmon was observed.Fairly good growth rates in flounder were observed in mixed culture experiments, but the flounder showed high individual variation. Fine meshed bottom net in the pen is necessary to retain enough food spillage to assure a positive growth rate in the flounder.

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1986.tb00429.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SummaryTwo different feeds in the initial period of adaptation of glass eels (Anguilla anguilla) to artificial food were examined. The difference between the experimental groups lay in the protein source: that of group A consisted of 50% fish meal and 50% chicken meal, and that of group B of fish meal alone.The mean weight of Gr. A was higher than that of Gr. B at the end of the experiment, and the percentage of larger elvers was higher (29%) than in group B (26%). It is concluded that 50% of the fish meal can be replaced by chicken meal, which is much cheaper in Israel and may also produce a slightly higher yield.

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1986.tb00430.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SummaryIn 152 isolated pairs ofTilapia mariaethe parents ate 41% of their broods before these reached the frees‐wimming stage. The cannibalized broods were usually eaten at the egg‐stage. Most brood‐eating was done by the males, as concluded from direct observations and from variation between males (but not between females) in the tendency of eat broods. Cannibalistic behaviour was more common when:1. the relative weight of female (female weight to male weight) was small (70 g)4. the pair spawned at certain times of the year (outside breeding peaks)5. the spawn was exceptionally small (less than 100 eggs).In normally sized spawns neither the number of eggs nor the size of the eggs or the spawn could be related to cannibalism. The probability of cannibalism was not altered in the second spawnings of the pairs after an experience of a first unsuccessful spawning. Many of these changes in frequency of cannibalism can be related to the males' expected reproductive success. Thus they possibly reflect an underlying natural adaptive variation which partly has been modified by the aquarium m

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1986.tb00431.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SummaryAge, growth and reproduction of rock gurnard in the Saronikos Gulf (Greece) were studied. Otoliths from 638 specimens (sex combined) were read for age determination. The body length‐otolith radius relationship was found linear (L = ‐18.0 + 4.99xR; where L = fish length in mm, R = otolith radius 20 X). The life span of females seemed to be longer than that of males, indicating a differential mortality with sex. The growth was lower than that in the Catalane Sea. The maximum age of fish collected was VIII and the maximum fork length estimated byvonBertalanffyequation was 356 mm. Weight increased as the 3.054252 power or the length. Reproduction was observed to take place between winter and early spring and occasionally in early winter. Males began to mature after completion of the second year and the females after the third. The exploitation rate was rather high, which suggests that the rock gurnard stock was overfished in Saronikos Gulf. The male to female ratio was usually

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1986.tb00432.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SummaryThe authors have experimental evidence that the protozoa causing the swimbladder inflammation (SBI) of the common carp (Cyprinus carpio) are indentical with presporogonic stages ofSphaerospora renicolaDyková et Lorn, 1982 parasitizing the renal tubules. Homogenates prepared from the thickened and inflamed swimbladder of naturally infected common carp, when injected into the abdominal cavity of fish, produced renal sphaerosporosis in the infection‐free common carp if the homogenates contained the parasites described by Kovács‐Gayeret al. (8). By intraperitoneal injection, the Unidentified Blood Organisms (UBOs) living in the blood of the common carp were transmissible to common carp, from the blood of which they were demonstrable for a long time. However, they were not transformed intoSphaerospora.To other cyprinids (gibel carp, silver carp, grass carp, tench, roach) neither the blood stages nor the swimbladder stages were transmissible from the common

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1986.tb00433.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Margolis, L. and Kabata, Z. (Editors):Guide to the Parasites of Fishes of Canada, PartBone, Q.; Marshall, N. B.:Biologie der Fische.Grundlagen der Fischpathologie.Advances in Anatomy, Embryology and Cell Biology.

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1986.tb00434.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY